In many public premises and such private premises where visitors have a fairly free access, there are spaces that require a certain type of behavior of the visitor. Among these spaces are for instance hospital treatment rooms and conference rooms in various institutes and enterprises. The behavioral requirements often relate to a mobile station and mean that the mobile station should be switched off or at least the ringing tone should be set to silent. It could be advisable to provide, for a person entering the room, at least an automatic notice of the recommendable behavior in the space in question. One possibility is simply to give a notice that the person has entered a certain room, without any specific instructions.
In the prior art there are known systems, based on different principles that are used for automatic space identification. They include a transmitter arranged in the space in question and a receiver that the user carries with him. The transmitter keeps sending a space identifier or tag signal, and a receiver that is located within the coverage of the transmitter detects the space tag and displays it in some form. The transmitter may represent the infrared type, in which case the intensity of the IR radiation is modulated by the space tag signal. FIG. 1 shows an example of this kind of solution. In the figure there is seen a conference room S1, on the rear wall whereof there is a tag transmitter 110. At the door of the room, a person M1 has arrived holding a receiver 120 in his hand. The infrared ray IRR from the transmitter 110 hits the receiver, which gives a sound alarm and for instance informs, in text form on the display, what is the nature of the space in question. A drawback with a system that uses infrared transmission is that the beam of the ray from the transmitter is fairly narrow, wherefore the transmitter is far from reaching a receiver in all spots throughout the space in question. The use of several transmitters can alleviate the problem, but this increases the expenses of the system.
The transmitter may also be a radio transmitter, in which case the radio carrier is modulated by the space tag signal. In that case the drawback is that the transmission easily proceeds to adjacent spaces, and the danger of erroneous messages is obvious. In addition, the devices are more expensive than infrared equipment. Moreover, the transmission can be realized purely inductively. The drawback of such a system is that in practice the range of an inductive transmitter remains within a few meters.
A common drawback with the described systems is that they require an installation of the transmitter and an arrangement of a power supply for the transmitter. In FIG. 1, power supply is represented by the cable 115. Moreover, the systems are unpractical because their use means that a receiver must be given to all persons entering from outside.
The object of the invention is to alleviate the described drawbacks connected to the prior art. The system according to the invention is characterized in what is set forth in the independent claim 1. The method according to the invention is characterized in what is set forth in the independent claim 11. Some preferred embodiments are described in the rest of the claims.